Nickel-free, low-alloy, high-strength steel



United States atent filice 2,858,206 Patented one. as, 1958 2,858,206 NICKEL-FREE, LOW-ALLQY, HIGH-STRENGTH STEEL 6 Claims. (c1. 75-126 This invention relates to a nickel-free, low-alloy, highstrength steel characterized in the quenched and tempered condition by the combination of good-notch toughness, as evidenced by a low transition temperature, and a high yield strength along with good Weldabiilty.

There 'is a need in mining, earth moving and similar equipment for a low-alloy, economical steel, combining high yield strength and good-notch toughness along with ready weldability in thicknesses up to I". It is desirable that such qualities be obtained with a minimum of expensive alloying elements such as molybdenum and without the use of the critical element nickel. We have discovered that a minimum yield strength of 90,000 p. s. i. and a transition temperature below -100 F. in plates up to 1" thick can be obtained in steel in the quenched and tempered condition within the following compositional ranges:

Percent Carbon 1 .12 to .21 Manganese .50 to 1.00 Phosphorus max .04 Sulphur max .04 Silicon .10 to .75 Copper to .50 Chromium .30to .75 Molybdenum .15 to .45 Vanadium .03 to .10 Titanium .01 to .03 Boron .0005 to .005

with the balance iron and residual impurities.

balance iron and residual impurities along with .25 to .35 copper if maximum corrosion resistance is desired. The following examples will illustrate the excellent properties obtainable with the steel of this invention.

A 1" thick plate with the following chemical composition, in percent, was water quenched from 1675" F. and then tempered for 1 hour at 1175 F.:

Heat B 0 M11 P S Si Cu Cr M0 V Ti After the aforementioned heat treatment, the mechanical properties of material at the center of the plate thickness were as follows:

Yield Tensile Elongation Reduction Transition Strength Strength, in 2 inches, of Area, Temperature, (0.2% Offset), p. s. i. Percent Percent F.

1 Keyhole-notched specimens.

It is apparent from these data that the steel of this invention possesses a high yield strength substantially in excess of 90,000 p. s. i. along with good notch toughness as evidenced by a transition temperature substantially below F.

The following heat illustrates that steel within the broad compositional limits outlined above will develop the desired properties, if properly heat treated, although not to as high a degree as steel within the preferred compositional limits:

Heat No. 0 Si Cr Mo V A /z and a 1" thick plate of this heat were hot rolled, quenched from 1675 F., and then the thick plate was tempered for 1 hour at 1175 F. and the 1" thick plate was tempered for 1 hour at 1100 F. A lower tempering temperature was used for the 1" thick plate than for the /2" thick plate because with the low alloy content, the 1" plate did not develop as much martensite at the center as did the /2 plate and with the low carbon and vanadium contents, the steel was less resistant to tempering than steels with higher carbon and vanadium contents. The mechanical properties representtaive of the centers of these two plates are as follows:

1 Keyhole-notchedspecimens.

is ISiihsize (0.252 diameter) specimens were used, therefore, elongation Thus, these data show that even with low alloy contents, the new steel can be heat-treated to develop high strength and good notch toughness, as evidenced by transition temperatures will below any ambient temperature that might be encountered in applications such as those for which the new steel is intended.

It should be noted that there is no copper in heat No. 2, yet the steel exhibits mechanical properties similar to those of the steel of heat No. 1, which steel contained 0.30% copper. Thus, copper, which was added for its known contribution to corrosion resistance, has little or no effect on the mechanical properties of the new steel, and can be added to or omitted from the steel, depending on the degree of corrosion resistance desired.

While we have shown and described several specific embodiments of our invention, it will be understood that these embodiments are merely for the purpose of illustration and description and that various other forms may be devised within the scope of our invention, as defined in the appended claims.

We claim:

1. A low-alloy, high-strength, nickel-free steel characterized in the tempered martensitic condition in thicknesses up to 1" by a yield strength in excess of 90,000 p. s. i. in combination with good-notch toughness as evidenced by a transition temperature below 100 F. and good weldability, said steel containing Percent Carbon .12 to .21 Manganese .50 to 1.00 Silicon .10 to .75 Copper to .50 Chromium .30 to .75 Molybdenum .15 to .45 Vanadium .03 to .10 Titanium .01 to .03 Boron .0005 to .005

with the balance iron and residual amounts of other elements. I

2. A low-alloy, high-strength, nickel-free steel characterized in the tempered martensitic condition in thicknesses up to 1" by a yield strength in excess of 90,000 p. s. i. in combination with good-notch toughness as evidenced by a transition temperature below -100 F. and good weldability, said steel containing Percent Carbon .14 to .18 Manganese .60 to 1.00 Silicon .15 to .35 Chromium .40 to .60 Molybdenum .15 to .25 Vanadium .03 to .07 Titanium .015 to .02 Boron .0015 to .003

balance iron, residual amounts of other elements and .25 to .35 copper.

3. A low-alloy, high-strength, nickel-free steel characterized in the tempered martensitic condition in thicknesses up to 1" by a yield strength in excess of 90,000 p. s. i. in combination with good-notch toughness as evidenced by a transition temperature below -100 F. and good weldability, said steel containing Percent Carbon .14 to .18

Manganese .60 to 1.00

Silicon .15 to .35

Chromium .40 to .60

Molybdenum .15 to .25

Vanadium .03 to .07

Titanium .015 to .02

- Boron .0015 to .003

balance iron and residual amounts of other elements.

4. Low-alloy, high-strength, nickel-free steel articles fabricated from plates of less than 1 thickness having a tempered martensitic microstructure characterized by a yield strength in excess of 90,000 p. s. i. in combination with good-notch toughness as evidenced by a transition temperature below 100 F. and good weldability, said steel containing with the balance iron and residual amounts of other elements.

5. Low-alloy, high-strength, nickel-free steel articles fabricated from plates of less than 1" thickness having a tempered martensitic microstructure chaarcterized by a yield strength in excess of 90,000 p. s. i. in combination with good-notch toughness as evidenced by a transition temperature below -100 F. and good weldability, said steel containing Percent Carbon .14 to .18 Manganese .60 to 1.00 Silicon .15 to .35 Chromium .40 to .60 Molybdenum .15 to .25 Vanadium .03 to .07 Titanium .015 to .02 Boron .0015 to .003

balance iron, residual amounts of other elements and .25 to 35% copper.

6. Low-alloy, high-strength, nickel-free steel articles fabricated from plates of less than 1" thickness having a tempered martensitic microstructure characterized by a yield strength in excess of 90,000 p. s. i. in combination with good-notch toughness as evidenced by a transition temperature below 100 F. and good weldability, said steel containing Percent Carbon .14 to .18 Manganese .60 to 1.00 Silicon .15 to .35 Chromium .40 to .60 Molybdenum .15 to .25 Vanadium .03 to .07 Titanium .015 to .02 Boron .0015 to .003

balance iron and residual amounts of other elements.

References Cited in the file of this patent UNITED STATES PATENTS 2,683,086 Clarke July 6, 1954 FOREIGN PATENTS 872,774 France June 18, 1942 OTHER REFERENCES The Iron Age, June 16, 1949, pages and 91.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Nos 2,858,206 October 28, 1958 Joseph F Boyce et a1.

- It is hereby certified that error appears in the printed specification of theabove numbered patent requiring correction and that the said Letters uld read as corrected below.

Patent sho Column 2, line 38, for "repreeentteive" read me representative lines 42 and 43, in the heading to the table, sixth ooln nn thereof, for ""Tenggereture, 1 F0" reed M Temperefloure FQ line 53, for will" read Well 0 Signed and sealed this 27th day of January 1959 1 "SEAL ittest? KARL HO-AXLINE a ROBERT C. WATSON Commissioner of Patents Atteeting Officer 

1. A LOW-ALLOY, HIGH-STRENGTH, NICKEL-FREE STEEL CHARACTERIZED IN THE TEMPERED MARTENSITIC CONDITION IN THICKNESSES UP TO 1" BY A YIELD STRENGTH IN EXCESS OF 90,000 P. S. I. IN COMBINATION WITH GOOD-NOTCH TOUGHNESS AS EVIDENCED BY A TRANSITION TEMPERATURE BELOW -100*F. AND GOOD WELDABILITY, SAID STEEL CONTAINING 